Figure 4. ¹H and ¹³C NMR spectra of (R)-diphosphomevalonate isotopomers.

Spectra indicate specificity and efficiency of labeling. Panel A. ¹H NMR spectra of labeled and unlabeled DPM. The efficiency and specificity of [²H₂]-labeling were estimated at >98% and >95%, respectively. Panel B. ¹³C NMR spectrum of [1-¹³C]DPM. The resonance at 181 ppm corresponds to C₁. The efficiency of labeling at C₁ is estimated at >92% (see Results and Discussion ). Based on the absence of non-C₁ signals and the S/N, the labeling specificity is calculated at >98%. Asterisks indicate instrumental artifacts.